A new digital textbook produced (free download here - classic public good characteristics!) by the CORE project. It looks very user friendly and covers some of the major economics theoretical (and applied) topics in an accessible way. Worth a read to the newcomer for sure.
New digital Economics textbook
Goes beyond A-level economics but a useful way of extending your Economics to low level undergraduate material - good for interview fodder to bolster the quality of your responses. It also has lots of great real world examples and analysis.